Electromagnetic fuel pump

ABSTRACT

In a plunger type electromagnetic fuel pump, a cost reduction is achieved by reducing a number of parts in conjunction with a layout of a check valve and making a cleaning step after assembling unnecessary. In an electromagnetic fuel pump ( 1 ) which pressure-feeds a fuel from a pressurizing chamber ( 6 ) formed on the front side of a plunger ( 3 ) by controlling a current application to an electromagnetic coil ( 5 ) and repeating generation and elimination of a magnetic force so as to slidably reciprocate the plunger ( 3 ) arranged in a cylinder ( 4 ), spring retaining members ( 36 ) provided with spring guides ( 361 ) retaining proximal end sides of return springs ( 33 ) urging valve members ( 32, 32 ) of check valves ( 30, 70 ) forming the pressurizing chamber ( 6 ) integrally has fixing structures for fixing them to mounting positions, and are fixed without using the other fixing means.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electromagnetic fuel pump used for delivering a liquid fuel reserved in a fuel tank to a combustion apparatus, more particularly to a plunger type electromagnetic fuel pump.

2. Description of Related Art

Conventionally, a fuel pump has been employed as a fuel delivery means of a combustion apparatus such as an oil heater, an engine or the like, and as described in Japanese Unexamined Patent Publication No. 5-79452 and Japanese Unexamined Patent Publication No. 2002-39067, there has been generally widely spread a plunger type electromagnetic fuel pump which can achieve a stable fuel delivery and an accurate flow rate control by repeating generation and elimination of a magnetic force to slidably reciprocate a plunger urged by a return spring for pressurizing a fuel in a fuel passage.

In the plunger type electromagnetic fuel pump, for example, as shown in a longitudinal cross sectional view, shown in FIG. 4, of an electromagnetic fuel pump 2 used for supplying a liquid fuel such as a gasoline or the like to an engine, a plunger 3 constituted by a magnetic material and arranged slidably in a cylinder 4 is moved backward on the basis of a magnetomotive force caused by a current application to an electromagnetic coil 5 against an urging force of a return spring 41, and a check valve 30 provided in a leading end side of the plunger 3 is opened so as to introduce the fuel into a pressurizing chamber 6 formed in a front side of the plunger 3 from an intake port 44 formed in a proximal end of the cylinder 4.

Further, the urging force of the return spring 41 overcomes the magnetic force by reducing or stopping the current to the electromagnetic coil 5, and the plunger 3 is moved forward, thereby pressurizing the fuel in the pressurizing chamber 6 and a check valve 70 arranged on the downstream side of the pressurizing chamber 6 is opened. The fuel is delivered toward the engine from a discharge port 42 formed in the leading end of the cylinder 4 by repeating the operation mentioned above.

In the plunger type electromagnetic fuel pump 2 for the gasoline engine mentioned above, as shown in an enlarged partial view of the plunger 3 in FIG. 5, the structure is such that the check valve 30 is provided in a leading end side (a discharge side) of a fuel passage 38 passing through the plunger 3, a valve member 32, a return spring 33 and a spring guide 34 are inserted, and the spring guide 34 is fixed to the plunger 3 by a fastening clip 35 corresponding to a fixing means having a repulsion force of a spring steel. Further, the check valve 70 having a check valve structure similar to the check valve 30 is provided in the cylinder 4 on the downstream side, and the pressurizing chamber 6 is formed between the check valves 30 and 70.

In this case, in a fixing structure of the valve members 32 and 32 constituting the conventional check valves 30 and 70 to the mounting position, the spring guide 34 and the fastening clip 35 for fixing the spring guide 34 are formed as separate parts, thereby causing an increase in a number of the parts of the electromagnetic fuel pump. Further, when the fastening clip 35 is inserted in the plunger 3 so as to be fixed, when manufacturing the electromagnetic fuel pump 2, there is a case that an inner peripheral surface of the mounting position of the plunger 3 is scraped by the fastening clip 35 and a chip is generated. Since there is a case that this causes a seat failure of the valve member 32, a cleaning step for removing the chip after assembling is necessary. Accordingly, these matters cause a cost increase of the electromagnetic fuel pump.

SUMMARY OF THE INVENTION

The present invention intends to solve the problem mentioned above, and an object of the present invention is to achieve a cost saving by reducing a number of parts relating to a layout of a check valve and making a cleaning step after assembling unnecessary, in a plunger type electromagnetic fuel pump.

In accordance with the present invention, there is provided an electromagnetic fuel pump comprising: a cylinder having a discharge port provided with a check valve and an intake port on a proximal end side thereof; a plunger slidably fitted in the cylinder, the plunger having a fuel passage formed along an axis thereof and provided with a check valve therein on a leading end side thereof; a return spring arranged on the proximal end side between the plunger and the cylinder for urging the plunder in a leading end side direction; and an electromagnetic coil arranged on the outside of the cylinder, a current application to the electromagnetic coil being controlled so as to repeat generation and elimination of a magnetic force to cause the plunger to slidably reciprocate for delivering a fuel under pressure; wherein at least the check valve provided in the plunger has a spring retaining member having a spring guide retaining a discharge side of the return spring urging a valve member thereof in a valve closing direction, and a fixing structure to the discharge port of the plunger or the cylinder.

As mentioned above, since the return spring guide retaining the valve member of the check valve via the return spring is integrally provided with the fixing structure for fixing it so as to form the spring retaining member, any fastening clip constituted by an independent part is not necessary as the fixing member, so that it is possible to avoid generation of a chip caused by an installation of the fastening clip as well as it is possible to reduce a number of the parts, thereby making a cleaning work after assembling unnecessary.

Further, in the case that the check valves provided with the spring retaining members are provided at two positions on an upstream side and on a downstream side of the pressurizing chamber, a delivery efficiency of the fuel is excellent and the parts reduction can be achieved at two positions.

Further, in the electromagnetic fuel pump mentioned above, in the case that the fixing structure of the spring retaining member comprises an outer peripheral side extending from the proximal end side of the spring guide in a centrifugal direction with respect to a center axis of the fuel passage, the outer peripheral side of the spring retaining member being fitted in an inner peripheral surface of the mounted position in close contact therewith, the spring retaining member being fixed on the basis of an elastic repulsion force of the fixing structure itself, it is possible to easily form by a comparatively simple structure.

Further, in the electromagnetic fuel pump mentioned above, in the case that the spring retaining member is made of a synthetic resin having an appropriate elasticity, it is easy to have a suitable elastic deformable performance as well as it is easier to form, and it is possible to easily and securely fix without requiring any high-level molding precision.

In accordance with the present invention in which the return spring guide retaining the check valve via the return spring is integrally provided with the fixing structure for fixing it to the mounting position, it is possible to omit the cleaning step after assembling as well as it is possible to reduce the number of the parts necessary in conjunction with the layout of the check valve, and it is possible to easily achieve the cost saving.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross sectional view showing an embodiment in accordance with the present invention;

FIG. 2 is an enlarged partial view of the leading end side of the plunger in FIG. 1;

FIG. 3A is a side elevational view of the spring retaining member, as seen from the upstream side of the fuel passage;

FIG. 3B is a cross sectional view, taken along the line X-X in FIG. 3A;

FIG. 4 is a longitudinal cross sectional view showing a prior art; and

FIG. 5 is an enlarged partial view of the leading end side of the plunger in FIG. 4.

DESCRIPTION OF PREFERRED EMBODIMENTS

The description will be given below of a best mode for carrying out the present invention with reference to the accompanying drawings.

FIG. 1 shows a longitudinal cross sectional view of an electromagnetic fuel pump 1, for example, in the case that the present invention is used in a fuel supply system of a gasoline engine. The electromagnetic fuel pump 1 delivers a fuel corresponding to a gasoline reserved in a fuel tank (not shown) so as to supply it to an engine via a fuel piping by an injector, and is called as a so-called cylinder type electromagnetic fuel pump.

The electromagnetic fuel pump 1 is structured such that an electromagnetic coil 5 is provided around a cylinder 4, and a plunger 3 is slidably arranged in the cylinder 4 so as to be slidable in a horizontal direction in the drawing. A return spring 41 is arranged on a rear end side of the plunger 3 in a compressed state, and urges the plunger 3 toward the downward side, i.e., toward the left in the drawing.

A fuel passage 38 passes through the center of the plunger 3 along the center axis thereof, a check valve 30 having a valve member 32 is arranged on a leading end side (a left side in the drawing), a check valve 70 having a valve member 32 is similarly provided on the downstream side of the check valve 30 and in a discharge port 42 provided in the cylinder 4 on the main body side and a pressurizing chamber 6 is formed between these two check valves 30 and 70. The above structure is similar to the conventional electromagnetic fuel pump and is well known.

Further, in the present embodiment, a spring retaining member 36 for retaining and guiding one end of a return spring 33 urging the valve member 32 in the valve closing direction integrally has a fixing structure for fixing it to the mounting position. In other words, as shown in an enlarged partial view of a leading end side (a discharge side) of the plunger 3 in FIG. 2, the spring retaining member 36 having a spring guide 361 retaining the proximal end side (left side in the drawing) of the return spring 33 integrally has a fixing structure formed by molding of a synthetic resin having an appropriate elasticity and fitted in the mounting position for fixing, and is fitted in the inner peripheral surface of the fuel passage 38 passing through the plunger 3 on the leading end side so as to be fixed, without using any fixing means as a separate part such as the fastening clip or the like as in the prior art.

As shown in FIG. 3A showing an enlarged side elevational view of the spring retaining member 36 as seen from the upstream side along the center axis of the fuel passage 38, the spring retaining member 36 is formed in an approximately disc shape as a whole, has four support arms 360 extending in a cross shape and pressing portions 362 arranged on the respective free ends of four support arms 360 for pressing and fixing the spring retaining member 36 so that the outer peripheral surface thereof is brought into close contact with the inner peripheral surface of the mounting position, with a gap formed therebetween for passing the fuel therethrough.

The outer diameter of the outer peripheral surface formed by four pressing portions 362 in an approximately circular shape is slightly larger than the inner diameter of the mounting position of the plunger 3, and the spring retaining member 36 is easily and firmly fixed to the mounting position while the resin material is elastically deformed, by pushing the spring retaining member 36 into the mounted position of the fuel passage 38 of the plunger 3 from the downstream side.

Further, as shown in FIG. 3B corresponding to a cross sectional view taken along the line X-X in FIG. 3A, the spring retaining member 36 has spring guides 361 on the respective support arms 360 on the upstream side thereof, thereby retaining the outer peripheral proximal end side of the return spring 33 and stably supporting the valve member 32 while urging it in the valve closing direction.

Further, the check valve 70 arranged on the downstream side of the pressurizing chamber 6 has the similar structure to that of the check valve 30 and achieves the similar operation and effect. Accordingly, in the present embodiment, since the synthetic resin spring retaining members 36 integrally provided with the respective fixing structures to the mounting position are arranged in two positions of the check valves 30 and 70 which form the pressurizing chamber 6, it is not necessary to use the fastening clip in conjunction with the layout of the check valve, and it is possible to largely reduce the number of the parts. However, it goes without saying that the present invention may be applied to at least one of them.

Further, since it is possible to securely fix the spring retaining member 36 to the mounting position without using the fixing means such as the fastening clip or the like, there is no risk that a chip is generated at a time of attaching as well as an assembling work is easily executed, so that a cleaning work after assembling is not necessary, and it is possible to widely reduce a labor hour and a cost for manufacturing. In this case, in the present embodiment, the description is given of the case that the present invention is applied to the fuel supply system of the gasoline engine, however, it goes without saying that the present invention can be applied to a fuel supply system of the other combustion apparatus such as an oil heater or the like.

As mentioned above, in accordance with the present invention, in the plunger type electromagnetic fuel pump, it is possible to reduce the number of the parts necessary in conjunction with the layout of the check valve, and it is possible to omit the cleaning step after assembling, whereby it is possible to achieve a cost reduction. 

1. An electromagnetic fuel pump comprising: a cylinder having a discharge port provided with a check valve and an intake port on a proximal end side thereof; a plunger slidably fitted in the cylinder, the plunger having a fuel passage formed along an axis thereof and provided with a check valve therein on a leading end side thereof; a return spring arranged on the proximal end side between the plunger and the cylinder for urging the plunder in a leading end side direction; and an electromagnetic coil arranged on the outside of the cylinder, a current application to the electromagnetic coil being controlled so as to repeat generation and elimination of a magnetic force to cause the plunder to slidably reciprocate for delivering a fuel under pressure; wherein at least the check valve provided in the plunger has a spring retaining member having a spring guide retaining a discharge side of the return spring urging a valve member thereof in a valve closing direction, and a fixing structure to the discharge port of the plunger or the cylinder.
 2. The electromagnetic fuel pump as claimed in claim 1, wherein the fixing structure of the spring retaining member comprises an outer peripheral side extending from the proximal end side of the spring guide in a centrifugal direction with respect to a center axis of the fuel passage, the outer peripheral side of the spring retaining member being fitted in an inner peripheral surface of the mounted position in close contact therewith, the spring retaining member being fixed on the basis of the elastic repulsion force of the fixing structure itself.
 3. The electromagnetic fuel pump as claimed in claim 1, wherein the spring retaining member is made of a synthetic resin having an appropriate elasticity.
 4. The electromagnetic fuel pump as claimed in claim 2, wherein the spring retaining member is made of a synthetic resin having an appropriate elasticity. 